Instrument Cluster Description and Operation: Tachometer

The instrument panel cluster (IPC) displays the engine speed as determined by the engine control module (ECM)/powertrain control module (PCM). The IPC receives a GMLAN message from the engine control module (ECM)/powertrain control module (PCM) indicating the engine speed. The IPC receives engine speed information from the body control module (BCM) via a GMLAN serial data message. The tachometer will default to 0 rpm if:

• The ECM/PCM detects a malfunction in the engine speed sensor circuit.
• The IPC detects a loss of GMLAN communications with the ECM/PCM.
• The IPC detects a loss of GMLAN communications with the BCM.